RE:SU Heavy sell volumes on US sideYep. I agree that it could be any/all of the things you mentioned.
I would add another one in that in the US there has been a lot of press about the Chevron approval re Venezuela and how Biden has turned his back on Canada, let alone the US oil business itself. There is increasing sentiment in the US with this latest development that if the Democrats stay on their current plan, it does not bode well for Canadian oil sands producers for at least the next couple of years. If this is a driver for the US action that you speak of, it has nothing to do with the SU announcement today and is more a longer term concern.